The present invention pertains to a device for the ultrasonic inspection of the weld seam of longitudinally welded pipes for longitudinal defects.
A device for the ultrasonic inspection of girth welds of pipes for longitudinal and transverse defects is published by Scott Lebsack and Helmut Heckhauser with the title “Immersion Probe Arrays for Rapid Pipeline Weld Inspection” in the journal Materials Evaluation (August 1995, pp. 886-891). This device has a holding system, in which two inspection head systems (arrays) are fastened. Each inspection head system has four inspection heads for inspection for longitudinal defects and one inspection head for inspection for transverse defects. The two inspection head systems for inspection for longitudinal defects are positioned on the right and left next to the girth weld, each inspection head acting as a transmitter and as a receiver at the same time, which detects a certain area of the seam in the direction of the depth.
The drawback of this prior-art device for inspecting girth welds is that it is not suitable for inspecting longitudinal welds of pipes for longitudinal defects, because no provisions are made for adapting the inspection head holder to the curvature of the pipe in case of arrangement in the circumferential direction of the pipe.
Moreover, it is not possible to reliably recognize all defects in the center of the weld due to the type of inspection with an inspection head acting as a transmitter and as a receiver at the same time. Longitudinal defects in the area of the center of the weld are detected by this technique only insufficiently if at all in case of greater wall thicknesses, e.g., >12.0 mm, precisely with the 45° inspection technique frequently specified in the inspection specifications, in which an acoustic irradiation angle of 45° relative to the pipe surface is specified.
DE 26 07 011 discloses a device for the ultrasonic inspection of the weld seam of submerged arc-welded large pipes, wherein at least four ultrasonic angle inspection heads are arranged on both sides of the weld seam and at different distances from the weld seam in an inspection area for inspection for longitudinal defects. One inspection head each on one side of the weld is located opposite another inspection head at equal distance from the weld on the other side of the weld. Each inspection head likewise acts as a transmitter and as a receiver of the ultrasound signal at the same time. The inspection area is determined by the series arrangement of the inspection heads along the weld seam, and the entire range of the weld thickness is to be covered by this series arrangement.
This device likewise has the above-described drawbacks of defect detection in the central area of the weld and additionally has the drawback that the device has a very complicated shape and adaptation to greatly different pipe diameters can be achieved in a highly complicated manner only.
Finally, reference shall be made to DE 101 34 696 C1, in which a device for the ultrasonic inspection of the weld seam of longitudinally welded pipes, among other things, for longitudinal defects, is likewise disclosed. This device also has an inspection head each, which acts as a transmitter and as a receiver at the same time, on each side of the weld, opposite each other, wherein flexible and rapid adaptation to different inspection tasks and pipe sizes is difficult due to the complicated shape of the device and the use of standard inspection heads.